1. Field of the Invention
The invention relates generally to a fire protection system for use in an air cleaning system and more particularly to a multicomponent fire protection system.
2. Description of the Related Art
Air cleaning systems have the potential of presenting serious fire hazards. Fires occur when three necessary components are present: oxygen, fuel, and heat. Air cleaning systems generally comprise a blower that forces a flow of air through one or more filter elements. The air flow contains an ample supply of oxygen, which means that this component of a fire hazard is always present in any air cleaning system.
Fuel is often present as well. The filter element itself often comprises combustible materials, for example cellulose, synthetics or cotton filter cloth. The dust particles being removed from the air flow oftentimes are combustible, in particular in industrial settings. Examples include welding fumes, saw dust; cotton dust; flour; and the like. The small particle size of these materials further exacerbates the problem. In many situations the air flow contains flammable liquids or vapors. For example, oils are used in welding and machining of metal components, for lubrication and for conservation or anti-oxidation of the work pieces. Oil enters the air flow in the form of vapor and small droplets. Oil becomes entrapped in dust covering the filter element, and is also adsorbed by the fibers of the filter cloth material. In addition, an oil film may develop on internal surfaces in the ducts of the air cleaning system, in particular upstream of the filter element.
Thus, oxygen, the first component needed for a fire, is present in virtually every air cleaning system. Fuel, the second component, is present in many air cleaning systems. Heat is not supposed to be present, but could enter the system, often in the form of sparks.
The main sources of sparks entering an air cleaning system include sparks entering the air cleaning system from outside the system, as commonly occurs in air cleaning systems for welding and machining operations. These sparks are formed with dry metal fabrication processes, such as welding, grinding, laser and plasma cutting and the like.
Various spark arrestors have been proposed for use in air cleaning systems for removing welding fumes.
U.S. Pat. No. 4,358,300 to Schlapman et al. discloses a spark trap including an internal baffle for reducing the velocity of the air stream passing through the trap. Particles settle out of the air stream into water contained in a water chamber at the bottom of the device.
U.S. Pat. No. 5,145,496 to Mellen discloses a multi-baffled flame arrestor positioned at the air inlet opening of a filter housing.
U.S. Pat. No. 6,626,984 to Taylor discloses a cylindrical filter element mounted within a cylindrical collector barrel so as to define an annular flow space between the two. A vane assembly is mounted at the top of the collector barrel for directing the incoming flow of air along a generally cyclonic path through the flow space, so that sparks and heavy particulates are forced outwardly away from the surface of the filter element, thereby increasing filter life and reducing the chance of fire.
U.S. Pat. No. 6,758,875 to Reid et al. discloses a robotic welding station with spark arrestor. The spark arrestor contains a baffle removably disposed on a housing for removing particulates from an air chamber.
U.S. Patent Application Publication 2010/0229727 to Barkdoll discloses a system for reducing the occurrence of fires in a fabric filter dust collection system. The system comprises a spark arrestor having a plurality of spaced-apart, wedge-shaped members having a gap between adjacent members sufficient to interrupt the flow of combustible particles from the source to the dust collection system.
U.S. Patent Application Publication 2006/0260286 to Schlebes et al. discloses a device for removing sparks or other hot particles from a gaseous stream. The device comprises a bulk ceramic or mineral material. The entire gaseous stream is forcibly guided through the bulk material such that the gaseous stream is substantially free from sparks after exiting the bulk material.
With the exception of the Schlebes et al reference, the general approach appears to be to make use of inertia for separating sparks from the gas stream, either by impinging the gas stream onto one or more baffles, or by forcing the gas stream into a cyclone pattern. Although sound in principle, this approach inevitably permits passage of smaller sparks, which may still contain enough heat to cause fire in the air cleaning system. Also, the components of these spark arrestors are exposed to contaminants of the air stream, such as oil, which makes regular cleaning a necessity. The design of the prior art spark arrestors makes cleaning difficult or even impossible.
The spark removal device of Schlebel et al. is designed to trap all sparks as may be present in the gas stream. It is clear that the device is also efficient in trapping oil, making the spark arrestor a fire hazard in its own right.
Thus, there is a need for an improved spark arrestor that efficiently separates sparks from an incoming air stream, yet is easy to clean.
There is a further need for a device capable of dosing particulate material, such as lime, into an air cleaning system
There is a further need for a fire protection system capable of preventing or dousing fires caused by incomplete spark removal.